Skip testing on Swift 5.8

Author: shahmishal

.github/workflows/pull_request.yml

@@ -10,6 +10,7 @@ jobs:
     uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@main
     with:
       linux_build_command: "swift build"
+      linux_exclude_swift_versions: '[{"swift_version": "5.8"}]'
       windows_build_command: "swift build"
   soundness:
     name: Soundness